On September 15, 2026, the US Court of Appeals for the Tenth Circuit ruled for the Army Corps of Engineers and Denver Water, lifting the remaining injunction on the Gross Reservoir Expansion. The opponents said they would not appeal. The ruling clears the way for Denver Water's largest storage project to move from construction to use.
A reservoir nearly three times larger
The project raises Gross Dam by 131 feet and expands the reservoir from about 42,000 to 119,000 acre-feet. Of the 77,000 acre-feet added, 72,000 are for Denver Water customers and 5,000 for an environmental pool. The dam raise was 95% complete in December 2025. Dam work is expected to continue into 2027 and reservoir preparation into 2028, with staged filling possible from 2028.
Why the north needed storage
Denver Water identified the need after the 2002 drought and Hayman fire. Its North System holds only 10% of total storage, which leaves the north side of the system with little room in dry years.
A project that survived a halt
A federal court halted construction on April 3, 2025, when the project was about 60% complete. The injunction was vacated on May 29, 2025, and work resumed. Denver Water has committed more than US$30 million to over 60 environmental mitigation and enhancement projects.
How Gross fits Denver Water's wider storage, treatment and demand strategy, and which programmes become the real test once construction ends, are examined in the second edition of the report. The full report, Water Utility of the Future: Denver Water, is available for USD 499 at https://ourfuturewaterintelligence.com/reports/water-utility-of-the-future-denver-water. For a free overview, read the Denver Water Utility Snapshot at https://ourfuturewaterintelligence.com/utilities/denver-water.